Synchronizing system



- Feb, 3, 1942, l.A EQCOLE E-rAL 2,271,625

' sYNcHRoNIzING SYSTEM Filed Aug. 2, 1939 3 Sheets-Sheet 1 Feb. 3, 1 E'COLE ETAL Y L l SYNCHRONIZING SYSTEM Filed Aug. 2, 1959 3 Sheets-Sheet-2POL Anlzeo MOTOR 8 SYN PERF ORA TOR Feb. 3, 1942. l. E.l com:v HAL2,271,625

VSYlCl-RONIZING' SYSTEM Filed Aug. 2, 1939 3 Sheets-Sheet 3 LE. COLE/A/VENTo/Ps:

A. E. MELHOSE Arron/Vey Patented Feb. 3, 1942 l SYN CHRONIZING SYSTEMIra E. Cole, Montclair, N. J., and Alfred E. Melhose, St. Albans, N. Y.,assignors to Bell Telephone Laboratories, Incorporated, New York, N. Y.,a corporation of NewYork Application August 2, 1939, Serial No. 287,926

15 Claims.

This invention relates to communication systems and particularly topermutation .code machine telegraph systems in which rotary distributorsare used at each end of a common channel to provide service for aplurality of telegraph channels.

An object of the invention is toprovide means for locking a receivingdevice out of service during idle times under such' control that itwillautomatically be restored to normal condition when the idle time hascome to an end.

In a system where synchronous distributors are kept in synchronism witheach other through the action of correcting means responding totransitions from one to another type of telegraph signal,

such for instance as a transition from a spacing ers at the distant endwill respond in a characteristic manner. Those on the channels where theidle time signals have not been changed will appear to be idle, butth'at on the one channel where the idle time signals have been changedwill respond by printing a long series of the same character or by noisymovements of some parts. If, for example, the normal idle time signalscomprise a series of spacing signals the receivers will respond in suchmanner that they appear idle, and if such normal idle time signals arechanged to a series of Vmarking signals, then the receivers will respondas though the code for letters is being repeatedly received. This causesa movement of parts and may be considered an annoyance if it occurs forany considerable length of v time.

A feature of this invention is a means for locking a receiver wh'ich isthus being operated out of service under control of means responding tothe those periods when the voice `has taken com- .io

mand and `there is consequently no telegraph transmission.

A feature of the invention is a slow releasing relay which is energizedthrough manual means by an attendant and is then held under control ofthe continuous and repeated reception of the code which causes themeaningless operation of the receiver, or if the system is incorporatedin an interpolated telephone and telegraph system, is held under controlof such telegraphic reception during periods of telegraphic use of thesystem and under control of the voice controlled switching means duringperiods of telephonie use of the system.

Another feature of the invention is a multicontact relay for severingthe connections between the receiving distributor and switching suchconnections to a slow releasing relay which is then held operated by theincoming telegraphic signals. When the character of the incoming signalschange, as when the operator at the distant end clears his tape in theusual way by sending a series of spacing signals, then the slowreleasing relay releases and returns the receiving circuits to normal.

Another feature of the invention is a signal which indicates when thetelegraph receiver is in circuit and when it is out of service.

Still another feature is a manual means for placing the receiver back inservice when it is being automatically held out of service. This may beused as a check, for if the attendant is in any doubt he may` releasethe automatic holding means and then when he iinds that conditions areproper, may again place the receiver out of service.

The drawings consist of three sheets, comprising Fig. 1 in the form of ablock schematic diagram and Figs. 2 and 3 in the form of circuitdiagrams illustrating the invention. With' Fig. 2 placed above and Fig.3 placed below Fig. 1, a complete .diagram illustrating the invention isformed.

Fig. 1 is a general schematic of a system in which theinvention may beemployed. A speech path l leads to a hybrid coil 2 from which a path 3for outgoing speech leads to a vogad 4. The outgoing speech then passesthrough a transmitting suppressor 5 and by means of an amplifierdetector 6 operates a chain of relays 1, here labeled as voice operatedswitching circuit. This voice operated switching circuit controls atransmitting singing suppressor 9 so that the outgoing speech can passfrom the transmitting suppressor 5 through the delay and amplifierB'andthe transmitting singing suppressor 9 to the hybrid coil I6. Fromthe hybrid coil IIJ the speech reaches another hybrid coil II and thencegoes through the radio transmitter to an antenna I3. Through radiotransmission, the speech will be received at some distant point and forpurposes of explanation it will be assumed that the distant point has areceiving circuit similar in all respects to the lower part of Fig. 1.The radio frequency modulated speech, therefore, enters antenna I4,passes through a radio receiver I5 and thence demodulated speech passesthe voice frequency repeater I6 to a hybrid coil I'I. From the hybridcoil I'I the speech goes into hybrid coil I8, thence through thereceiving singing suppressorl I9, the receiving repeater 26, a low-passfilter 2| and a path 22 to a hybrid coil, such as 2, whence it goes tothe receiving subscriber over a line, such as I.

The Voice operated switching circuit T controls a control tone enabler23 through the contact and armature of the relay 89 so that a source ofcontrol tone 24 is passed through the control tone compressor |26 andthe control tone filter 25 to the hybrid coil II and thus accompaniesspeech. The voice operated switching circuit 1 also controls a switchingpoint leading from the receiving switching circuit 26 at the sameterminal to the transmitting suppressor 5 so as to open this circuitduring the periods that speech is going out from line I to antenna I3.During this time the voice operated switching circuit I also controlsthe telegraph control circuit ,shown in Fig. 2 by operating relay I04-inorder to stop the action of the telegraph transmitting circuit duringthe time the voice is being transmitted from line I out over antenna I3by the usual modulation means.

At the receiving end the control tone with the usual modulation of thecarrier frequency coming in over antenna I4 is demodulated in radioreceiver I5 and passes through the hybrid coil I'I and thence through atelegraph band elimination filter 28 and into a control tone amplifierand filter 29. This operates the receiving switching circuit 26 whichperforms several functions as follows: first, the receiving switchingcircuit 26 controls a normally open circuit between the telegraph bandelimination filter 28 and the receiving switching circuit 26, includinga speech amplifier 30 so that when control tone is first received theswitching circuit 26 will be operated thereby and then held operatedthereafter by speech currents flowing through the amplifier 30. When thecontrol tone is first transmited it goes out into antenna I3 at highVolume but after an interval determined by the delay introduced by thedelay and amplifier 8 the speech operates a compressor |26 `to reducethe volume of the control tone to avoid overloading-the radiotransmitter I2 by the combination of control tone and speech. This, ofcourse, operates to advantage at the receiving end by giving an impulseof great strength through the control tone amplifier and filter 29 tooperate the circuit 26 before the path through the speech amplifier 30is closed.

The receiving switching circuitV also controls the receiving singingsuppresor I9 to open up the speech path. The receiving switching circuit26 also controls a normally closed path between the band-pass filter 3land the telegrad 32 so that, while speech is being received, thetelegrad 32 will be disabled. Atthe same time, the receiving switchingcircuit 2,6 controls the switching relay 33 for two telegraph channels.

During pauses in the speech, either when the subscriber at the distantend is talking into channel I or during the time when the subscriber onchannel I pauses during his talk out over the antenna I3, the telegraphapparatus shown in Fig. 2 is in operation. This comprises perforators 6Iand 35 working respectively into tape transmitters 63 and 95 and thenceinto the rotary distributor shown in the upper right-hand corner of Fig.2 and here designated generally by the numeral 64, indicating the motorand synchronous equipment for driving such distributor. The rotarydistributor works through the control circuit comprising various relaysof Fig. 2 and by means of relay 'I9 controls the telegraph signalconverter 39. 'This signal converter is a circuit controlling devicedisclosed in Patent 1,749,851 to H. C. Silent, March 11, 1930. When therelay I9 is on its marking contact, then the telegraph signal converteris in such a condition that alternating current coming from thetelegraph signal oscillator 40 passes freely into hybrid coil I0 fortransmission out over the antenna I3. When the relay 'I9 has itsarmature driven to its spacing contact, then the suppressor action oftelegraph signal converter 39 blocks off the telegraph signaling currentand nocurrent will, therefore, get into hybrid coil I0.

At the distant end these telegraph signals in the form of spurts ofalternating current of the usual form of a carrier of the oscillatorfrequency with side-bands about seventy cycles Wide caused by themodulation of the carrier by the telegraph transmitter are received overantenna I4 by the radio receiver I5 and thence through the repeater I6whence they pass through the hybrid coils II and I8 to the band-passfilter 3|. Thereafter the signals enter the telegrad 32 and areconverted from varying strength alternating current signals touniformstrength direct current signals of practically the same strengthat which they were received over the antenna I4. For a completedescription of the telegrad, reference is made to application Serial No.283,368, filed July 8, 1939 by Barney et al. These direct currentsignals then pass through the switching relay circuit to Fig. 3 andtherotary distributor 4I tothe two printers 42 and 43. During the receptionof telegraph signals .the receiving switching circuit 26 is unoperatedand the speech path is blocked off by the receiving singing suppressorI4.

The rotary distributor I4 is kept in synchronism with the distant rotarydistributor of Fig. 2 by means generally described in the Cole et al.Patent No. 2,207,720, dated July 16, 1940, and in particular by themeans disclosed in a patent granted to L. A. Meacham No. 2,207,748,dated July 16, 1940i.

For purposes of thekpresent description, it is only necessary to mentionthe fact that the rotary distributor 4I. will be kept in perfectsynchronism with the distributor ,of Fig. 2 if there is an occasionaltransition from a spacing to a marking impulse, that is, if there is anoccasional operation of the relay 19. Such transitions are caused duringthe normal operation of either the A channel or the B channel,.hererepresented by tape transmitters 63 and 95, respectively. If there is astoppage of transmission over both channels at the same time so thatneither transmitter 63 nor transmitter 95 is in operation, then themeans of the present invention is provided to cause an occasionaloperation of the relay 19. Specifically, as shown, the relay 'I9`will gothrough one cycle of operations per cycle of operation of the rotarydistributor of Fig.'2.

In operation, if no voice currents are being transmitted'from line andthe voice operated circuit, therefore, is unoperated, the telegraphapparatus of Fig. 2 will be fully enabled with relay |84 in the positionshown.

The tape transmitter 63 has ve pins, such as 13, which will engageperforations in the tape 62. When this occurs, the contact 1li is movedfrom its lower contact 15 to its upper contact 16. The upper contact 16represents a marking condition and the lower contact 15 represents aspacing condition. When in the course of operation of the distributorthe shaft 65 brings a brush into position to make the contact betweensegment 11 and ring 18, either spacing current from contact 15 ormarking current from contact 16 will be extended through the telegraphtransmitting line relay 19. If marking current is transmitted, then thepolar relay 19 will be left in the position shown, whereby thesecondaries of transformers 54 and 55 are closed and the tone fromsource 49 is transmitted into the hybrid coil I and thereafter out overantenna |3. If spacing current is transmitted through the relay 19, thenthe armature will move to the left and the suppressing action of thetelegraph signal converter 39 will prevent any tone being transmittedinto the hybrid coil l0, thus establishing a spacing signal condition.

Let us assume that the shaft 65 is just coming to a position Where itwill make a connection from segment 80 to ring 8| and where the brushworking on ring 18 will successively pass over the segments 82, 83, 84,85 and 11, comprising the five code segments from the channel Atransmitter. Under the assumption that the voice circuit is not actuatedat this time, the relays 86, 81, 88 and 89 will be in the positionsshown. As just previously mentioned, a connection has been made betweenring 90 and segment 9|, thus connecting g-round to the lower winding ofrelay 92. Relay 92 will then have moved its contact to the positionshown so that battery is connected to one side of the stepping magnet'93in the channel A tape transmitter 63. This magnet `is not energized atthis time. Since relay 81 is in the position shown, the connectionbetween common ring 8| and segment 88 is ineffective and, therefore,relay 92 isv left in the position shown. Now, as the brush successivelypasses over segments 82, 83, 84, 85 and 11, the marking or spacingsignal current, as the case may be, is transmitted through the backcontact and a-rmature of relay 98 to the contact and armature of relay86, winding of relay 19, to the common point of the marking and spacingbatteries.

As the brushes connected to shaft 65 pass further along and are now inthe position of transferring the record from tape transmitter 95, aconnecti-on will be made from ring 96 to segment 91 and thence to theother side of stepping magnet 93 so that, while the record from tapetransmitter 95 is being transmitted, the shaft 98 of tape transmitter 63will be rotated and the tape advanced to the next set of codeperforations. In a similar manner, during the movement of the shaft 65,a connection will be made to segment 99 while the record from tapetransmitter 63- isbeing transmitter and shaft |98 will be rotatedthrough the energization of magnet IDI. In this manner the record of thetwo transmitters will be alternately transmitted by the relay 19.

Let it be assumed now that there is a stoppage 38 leading in parallel tothe two windings of relay 31. These windings, however, are equal andopposed so that the relay 31 does not become operated at this time.However, when the taut tape switch 3.6 is operated, then the next timethat connection is made between the ring 96 and the segment 21 theright-hand winding of relay 31 alone will be energized and, since thereis now no opposing force, the relay 31 will operate and through itsright-hand armature and front con` tact will lock in an operatedposition. The lefthand armatures of this multicontact relay 31 nowtransfer the tape transmitter contacts from the distributor contacts 56,51, 58, 59 and 68 to conductor 44, leading to the marking battery.Therefore,l as long as relay 31 is operated, the telegraph transmittingline relay 19 will be driven to its marking contact While the brush onshaft is passing over segments 56 to 68, inclusive.

If during this time the channel A becomes idl then spacing current willbe connected to the segments 82, 83, 84, and 11 and hence the telegraphtransmitting line relay 19 will send out rst ve spacing signals and thenve marking signals andl will repeat this operation as long as there isstoppage of transmission on both channels. Thus, there will be at leastone transition from a spacing to a marking impulse per cycle ofoperation of the rotary distributor.

When transmission is resumed on channel B, the perforation of more tapewill cause the taut tape switch 36 to operate to the position shown and,hence, when the brush of the rotary distributor again makes contactbetween ring 96 and segment 21, the left-hand winding of relay 31 willbe energized. Since the right-hand winding is already energized, theresult will be equal and opposed and therelay 31 will becomedeenergized. Therefore, as the shaft 65 of the rotary distributorproceeds and the segments 56 to 69 are reached, normal conditions willexist and proper transmission of the codes will take place.

The operations of the relay 86 to 89, inclusive, are fully explained inthe Cole et al. Patent No. 2,220,889, dated Nov. 11, 1940. In general,when the voice takes command of the circuit and the voice operatingcircuit 1 is operated, then relay |84 becomes operated and, in turn,causes the operation of relays 86 and 81. Thereupon the transmission oftelegraph signals is stopped through the operation of relay 92 and itscompanion relay |85, which prevent the operation of the stepping magnets93 and l8l, respectively.

If the transmission of code is at a critical point, as when a connectionis being made between ring |08 and segment |01, the relays 88 and 89will be operated so as to prevent the operation of relay .|94 fromoperating the relays 86 and 81 to stop the transmission of a telegraphcode. This condition, however, lasts for only a very short interval andrelays 88 and 89 will return to normal so that relays 86 and 81 maybecome operated in the usual manner.

At the receiving end, the telegraph pulses coming in over antenna I4will pass through hybrid coils I1 and I8 and the band-pass filter 3| tothe telegrad 32 where they will be changed to direct current impulses ina manner fully described in the aforementioned Barney et al.application. The result will be that relay 46, known as the receivingtelegraph master relay, will be driven to the position shown for eachmarking impulse and will be driven to the opposite position for eachspacing impulse.

Relay 41 is controlled by the receiving switching circuit 26 so thatduring the periods of telegraph transmission this relay will be operatedand consequently relays 48 and 49 will be released and in the positionshown. Therefore, each marking impulse will result in the operation ofthe chain of relays 50, and 52.

Relay 50 extends a ground connection through its armature to thedistributor ring 53 and as the brush mounted on the shaft 66 movesforward the printer magnets 61, 68, 69, and 1| will be operatedaccording to the code being received by the receiving telegraph masterrelay 46. The operation of auxiliary relay 5| during a marking impulsecloses a connection from ground through its armature and marking contactto ring |29 and thence to segment 12 through the appropriate brush onshaft 66 to the lower winding of relay 33 to positive battery. Thisdrives relay 33 to its marking contact, as shown, and since this is apolar relay and will keep its armature where last placed until it isenergized in the opposite direction, this relay will remain as shownuntil relay 49 is energized. Now as the shaft 66 moves along and iscontrolling the set of selecting magnets of channel B printer 43 aconnection will be made between the ring |21 and segment |28 through thearmature and contact of relay 33 to cause the energization of printermagnet |03. If shaft 66 gets beyond the ve small segments connectingselecting magnets 61 to 1|, inclusive, the relay 88 cannot be driven toits spacing contact again until the shaft gets back to near the positionshown.

Thus, while the selecting magnets of printer A are being set theprinting magnet |02 will be operated, and while the selecting magnets ofchannel B printer are being selectively operated the printing magnet 63of channel A printer will be operated.

In a manner fully described in the Cole Patent No. 2,220,889, relay 41moves to the position shown when voice currents take command of thevoice operated switching circuit 26. At that time relays 48 and 49become operated. Relay 48 drives all of the relays 50, 5| and 52 totheir spacing contacts and relay 49 closes at appropriate timesconnections from ring |96 through segments |09 and IIiJ to drive therelays 33 and to their spacing contacts through their lower windings.Hence, as soon as the voice takes command the printers are disabled.

With relay 52 on its spacing contact, a connection is established forcharging condenser I2. Whenever there is a transition from a spacing toa marking signal, condenser ||2 is discharged through the markingcontact of relay 52 and ring ||3 into segments leading either to theupper or the lower winding of relay I I4. If the distributor is inprfect synchronism, then the condenser ||2 will discharge practically asthe brush is passing from a segment leading to one winding of relay |I4and on to asegment leading to the other winding of relay H4, with theresult that relay I4 remains idle. With the least unbalance, however,relay I I4 operates to its right or its left contact momentarily. As theseverity of the unbalance increases the action of relay |I4 becomes moredecided, with the result that the fast relay ||5 or the slow relay ||6becomes operated. In the present case an indicator ||1 is shown and thiswill be operated to indicate that the distributor 4| is running eitherfast or slow.

The indicator ||1 is here used merely to illustrate means fullydescribed in the application to Meacham Patent No. 2,207,748, whereby acorrection in the speed of the distributor is made. So long as bothchannels are working, or so long as either channel is working, therewill be an occasional transition from spacing to marking and hence therewill be an occasional correcting impulse. In the case of stoppage oftransmission on both channels, then the printer 42 will continuouslyreceive five spacing impulses, with the result that no operation willtake place. The printer B, however, due to the operation of the tauttape switch 36 of Fig. 2, will continuously receive ve marking impulses.This is the code for Letters and will result only in operating certainmechanism in the printer which will cause a sound which, if repeated toomany times, may become annoying. If the repeated operation of theLetters mechanism does become annoying to the operator, then the specialmeans of the present invention is provided.

The operator at printer B may lock out this printer by once operatingthe manual key ||8. If the switch ||9 is thrown to its upper position,then a circuit will be established from ground, switch I 9, the lowertemporarily closed contacts of key ||8, the contacts of Vkey I2|), thewinding of relay I2|, through the upper temporarily closed contacts ofkey ||8 to negative battery. Relay I2| locks in a circuit from negativebattery, the left-hand armature and front contact of relay |2|, thecontacts of key |29 to the trunk contacts of relay |22. Relay |22 isoperated through the right-hand armature and front contact of relay I2|and this relay now transfers`l the distributor contacts for channel Bfrom the selecting magnets of channel B to the winding of relay I2|.Relay I2| is slow to release and as long as marking impulses are comingin, relay |2| will remain operated.

If the voice takes command of the receiving switching circuit 26, thenrelay 41 will be released, with the result that relay 49 will now becomeoperated. While relay 49 is unoperated a circuit through its backcontact causes the operation of relay |23 but when relay 49 becomesoperated, relay |23 releases and holds relay I2| operated during theperiods in which the voice has control of the system and the telegraphreceiving apparatus is disabled.

When telegraph transmission is resumed over channel B it is the usualpractice for the operator thereat to send a series of spaces in order toclear his tape. This will result in the transmission of a series ofspacing impulses, with the result that the slow-operating relay 2| willbecome released. This in turn releases the multicontact relay |22 sothat the channel B printer is again put into operative condition.

As an alternative arrangement, the switch 49 may be moved to its lowercontact and hence the original circuit for the energization of relay I2|will be closed only when the brush on shaft 66 makes contact betweenring |21 and segment |24. This arrangement is made for reasons toprevent a possible error which might appear if the key I8 were pressedafter one or more, but not all. of

of servicev to prevent annoyance. operator desire to check conditions,khe may operthe selecting magnets of the channel B printer had been setby marking impulses. Any such error which might appear would beinconsequential, so that the` arrangement including ,the

.segment |24 is a refinement to a high degree.'

dition and when the lamp `is extinguishedit will indicate that thechannel B printeris Alocked out Should the ate key |20. This will causerelay |2| to restore,

with the result that channel B lprinter will *be put back into service.If the operator'observes a repeated Letters function, he may again presskey ||8 to lock this-printer out of service and it will be automaticallyplaced back in operative condition inthe manner hereinbefore described.

It is to be understood that the present invention -is not to be limitedto the specic manner o f pro- I-nentlyinverted channel might be employedor a vmanual means for producing ,marking instead of spacing impulsesduring idle periods on one channel might be used.

What is claimed is:

l. In a communication system, .a receiving'terminal comp-risingtelephone and telegraph receiving means and speech controlled switchingmeans for lalternatively rendering either the said -telephone or thetelegraph means eiective, said telegraph means including permutationco'de responsive means and means for locking said last means out ofservice under control of the repeated reception of a particularpermutation code during intervals of eiectiveV telegraphic reception andunder control of said switching means during intervals of effectivetelephonic reception.

2. In a communication system, a receiving terminal comprising telephoneand telegraph receiving means and speech controlled switching means foralternatively rendering either the said telephone or telegraph meanseffective, said telegraph means including permutation code responsivemeans, means for manually switching said last means out of service, andmeans for thereafter holding said permutation code responsive means outof service under control of the repeated reception of a particularpermutation code.

during intervals of effective telegraphic reception and under control ofsaid speech controlled switching means during intervals of effectivetelephonic reception.

3. In a communication system, a receiving distributor, a plurality ofsegments on said distributor leading to a receiving device, means fordisconnecting said segments from said receiving device and connectingthem to a slow releasing relay, and means under control of said slowreleasing relay for maintaining said changed connections responsive tothe continued and repeated reception of signals over said distributorsegments.

4. In a communication system, a receiving terminal comprising telephoneand telegraph receiving means and speech controlled switching means foralternatively rendering either the said telephone or telegraph meanseffective, said telegraph means including a synchronous distributorhaving a plurality of segments leading to a receivingdevice, amulticontact relay for switching said segments from said receivingdevice to a lslowrel'easing relay, saidslow releasing relay, manuallmeans Afor iirst 'operating said slow re- Ileasingnrelay, meansincluding said connections to -said 'segments effective duringyintervals of telegraphjic reception and said first switching .meanseffective during intervals of telephonie reception for holding said slowreleasing relay operated, Aand m'eans under .contr-ol Aof said slowreleasingA relay for Voperating said multicontact relay.

5. In a communication system, a receiving terminal comprisingtelephoneand telegraph receiving means and speech controlled switching means foralternatively` rendering either the said, telephone -or' telegraph meanseffective, said telegraph means ncluding, a synchronous distributorhaving a :plurality of segments leading to a receiving device, amulticontact relay for switching -said segmentsfrom saidreceiving deviceto a slovvv releasing relay, .said slow releasing relay, manual meansfor lrstoperating said slow releasing yrelay, means including saidconnections to said segments efective fduring intervals of 'telegraphicreception and said rst switching means eifective duringintervals oftelephonie receptionf'for holding said vslow releasing Arelay operated,means under control of said slow releasing relay Ior operating saidmulticontact relay, and a visual signalfor indicating that saiddistributorsegments aref connected to sa-id receiving device .l

6. I-n` a `communication system, a communica- `tion channel, 'means forcommunicating over said Achannel by telephonel and by telegraph, Avoiceresponsive- `means for switching Y terminal apparatus Yfrciifn telegraphtransmitting and'receiving "apparatus to telephone transmitting andreceiving apparatus, a pair of synchronous distributors at the ends ofsaid channel for cooperating with said telegraph transmitting andreceiving apparatus, said telegraph apparatus including saiddistributors comprising a plurality of telegraph channels, correctingmeans for said distributor at the receiving end of said channelresponsive to transitions from one to another type of telegraph signal,means at the transmitting end of said channel responsive to stoppage oftelegraph communication for changing the normal idle time telegraphsignals on one of said telegraph channels to provide at least oneeiective transition -per cyclev of operation of said distributors, andmeans at the receiving end of said channel for locking the receivingtelegraph apparatus on the said channel on which said normal idle timetelegraph signals have been changed out of service under control of saidchanged signals and said terminal switching apparatus means.

'1. In a communication system, permutation code responsive receivingmeans, means for locking said permutation code receiving means to betion code combination for restoring said means to code receivingrelation.

9. In a permutation code receiving system, permutation code responsivereceiving means, means for locking said means out of service, a visualsignal for indicating when and Whether said means is in service, meansoperative under the control of selected code combinations for restoringsaid means to service.

10. In a combination, a permutation cod-e receiving channel, a codeinterpreting device operative to receive and interpret repeatedidentical code combinations received over said channel, means forlocking the code interpreting device out of service, means formaintaining it out of service during repeated reception of said codecombinations, and means operative under the control of selected codecombinations to restore said device to service.

11. In a telegraph code receiving channel,A

means for receiving and distributing permutation code impulses, a codeinterpreting device for said impulses, means for locking said device outof code interpreting relation during reception of an indefinite train ofcode combinations, and means for restoring said device to service undercontrol of other selected code combinations.

12iI In a receiving system comprising distributing apparatus designed tooperate synchronous- 1y in relation to incoming impulses, means` pulsesupon said channel to unlock said locking means.

13. In a system of telegraphic transmission, wherein application ofvoice signals to said system suspends the telegraphic transmission, areceiving instrument for telegraphic impulses, means for locking saidinstrument out of telegraphic impulse receiving relation during periodsof telegraphic reception, and means controlled by voice reception formaintaining said device locked out of telegraphic receiving relation, incombination with instrumentalities operating under the control oftelegraphic code combinations for removing said device from control ofeither of said locking means.

14. A channel of telegraphic reception comprising distributing means anda code interpreting instrument supplied thereby, in combination Withmeans for locking said code interpreting instrument out of operationunder the control of an indefinite train of marking impulses, and meansfor restoring said device to code interpreting relation under thecontrol of an indeiinite train of spacing impulses.

l5. In a signaling system comprising a transmission channel, telegraphapparatus associated with a receiving end thereof and adapted to receivesignals in the telephone frequency range, telephone apparatus adapted tobe associated With said channel, means for automatically disconnectingthe telegraph apparatus from said receiving end and connecting thetelephone apparatus thereto on arrival on telephone currents, and meansfor locking said telegraph apparatus in non-responsive relation toreceived telegraph impulses during the reception of synchronizingtelegraph impulses.

IRAELCOLE. ALFRED E. MELHOSF.

